In the various technology fields such as a display field, a solar cell field, a touch panel field etc., an oxide thin film has been used as the electric component of device. The main advantage of the oxide thin film is known that it can provide thin film with high electric conductance as well as high transparence.
As a material of this oxide thin film, Zinc oxide (ZnO), Indium zinc oxide (IZO), and Indium gallium zinc oxide (IGZO) and so on have been researched. Recently, Zn (Zinc), Sn (Tin), Ti (Titanium) has been investigated as an alternative material of Indium in order to improve the economic efficiency of the device manufacturing.
In the meantime, vacuum deposition equipment including a target etc. has been a dominant process in oxide thin film deposition. But recently the researches about the oxide thin film forming method using the solution process have been conducted for the low cost process.
But the method using the solution process has several weak points. For example, it requires a thermal process at the high temperature more than 300° C. during the manufacturing process. The reasons are listed below. Firstly, the high temperature treatment is needed for removing organic solution in the oxide solution. Secondly, it is for generating oxidizing substances inducing reaction between the metallic material and oxygen and has the specific functional (the conductor, the semiconductor, the insulator property etc.). Thirdly, it is to remove the impurities which deteriorate the film quality with the combination of the oxidizing substances.
Regarding the thermal treatment during the solution process, the thermal treatment at the high temperature increases the manufacturing cost of the oxide thin film. Moreover, thermal process at the high temperature may cause the deformation of the substrate, especially, in case of plastic substrate, textile material and so on, whose melting points are relatively low. It is crucial factor for application of flexible electronic device.
To solve the problem, the research about annealing the oxide film at low temperature has been performed. One example of these researches is that the oxide film is annealed at the vacuum environment at lower thermal annealing temperature. But in case of vacuum process, there are several disadvantages such as the non-uniformity, performance degradation, as well as a rise of manufacturing cost. Moreover, the temperature also has the lower limit of about 230° C. level. Even if the lower temperature is possible, the impurities cannot be fully removed, which makes the performance of the oxide thin film easily degraded.
In order to solve these problems, when the oxide thin film is formed using solution process, the annealing process using the laser has been suggested. U.S. Pat. No. 7,208,401A and US2008/0057631 etc. are the examples. The prior arts disclose the technology which irradiates the oxide solution layer with the laser light at the atmosphere. But, the prior art couldn't achieve an oxide thin film with a good performance. In other words, there has been no research with a good performance about irradiating the oxide solution layer with the laser light. We also tried to manufacture the oxide thin film according to prior arts. But, we weren't able to achieve the quality applicable to electronic device.